Mercurial > dive4elements > river
view flys-artifacts/src/main/java/de/intevation/flys/artifacts/math/fitting/InvQuad.java @ 3903:0623cdf32b38
Document issue880
flys-artifacts/trunk@5568 c6561f87-3c4e-4783-a992-168aeb5c3f6f
author | Felix Wolfsteller <felix.wolfsteller@intevation.de> |
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date | Sat, 22 Sep 2012 09:55:01 +0000 |
parents | de67497de5a0 |
children |
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package de.intevation.flys.artifacts.math.fitting; public class InvQuad extends Function { public static final Derivative DERIVATIVE = new Derivative("Q'(W) = 1/sqrt(4*n*(W-b)+m^2)") { @Override public de.intevation.flys.artifacts.math.Function instantiate(double [] parameters) { double n = parameters[0]; double m = parameters[1]; final double b = parameters[2]; final double n4 = 4d*n; final double mm = m*m; return new de.intevation.flys.artifacts.math.Function() { @Override public double value(double W) { return 1d/Math.sqrt(n4*(W-b)+mm); } }; } }; public static final Function INSTANCE = new InvQuad(); public InvQuad() { super( "inv-quad", "(sqrt(4*n*W-4*b*n+m^2)-m)/(2*n)", new String [] { "n", "m", "b" }); } @Override public double value(double W, double [] parameters) { double n = parameters[0]; double m = parameters[1]; double b = parameters[2]; return (Math.sqrt(4d*n*(W - b) + m*m)-m)/(2d*n); } @Override public double [] gradient(double W, double [] parameters) { double n = parameters[0]; double m = parameters[1]; double b = parameters[2]; double Wb = W-b; double sn4Wb = Math.sqrt(4d*n*Wb + m*m); return new double [] { Wb/(n*sn4Wb)-(sn4Wb-m)/(2d*n*n), (m/sn4Wb-1d)/(2d*n), -1d/sn4Wb }; } @Override public Derivative getDerivative() { return DERIVATIVE; } @Override public Function getInverse() { return Quad.INSTANCE; } } // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 :